Chondromyxoid fibroma (CMF) is one of the rarest of bone tumors, accounting for less than 1% of all bone tumors.

It is a benign (noncancerous) tumor that most often develops in older children and young adults under 30 years of age. CMF is found equally in both males and females.

Treatment for CMF requires surgery to remove the tumor.

Description

Chondromyxoid fibroma grows out of the cartilage-forming tissue found in the marrow of bones ("chondro" means cartilage). It typically develops in the flared end of a long bone in the lower body, such as the tibia (shinbone) or femur (thighbone). The most common location of CMF is in the tibia near the knee, Other common locations include the femur near the knee, the bones of the foot, and the pelvis (hip area).

CMF does not metastasize (spread) to other parts of the body.

(Left) Normal knee anatomy. (Center) This x-ray shows a CMF tumor near the end of the tibia. (Right) This x-ray provides a side view of the same CMF tumor.

People with chondromyxoid fibroma may be able to feel a bony lump at the location of the tumor. There may be mild to severe pain associated with the bump, or there may be no pain at all. In some cases, there is no bony bump, just a varied amount of pain in the area of the tumor.

Medical History and Physical Examination

There are many aspects to the doctor's examination. Before a physical examination, your doctor will talk with you about your general health, as well as your symptoms in order to get a good history of the problem. Pain at night or at rest, or pain that just does not go away is more typical of tumors in general, and CMF in particular. In contrast, pain from an injury usually decreases when the injured area is not moving.

During the physical examination, your doctor will look for tenderness over the bone and check your range of motion in the area of your pain.

Tests

In order to diagnose CMF, your doctor will order imaging and tissue tests.

X-rays. These tests create clear pictures of dense structures like bone, and are very helpful in diagnosing CMF. Most chondromyxoid fibromas are small (1 to 4 cm), round- or oval-shaped tumors. In x-rays, they are often surrounded by a white (sclerotic) rim.

In many cases, the tumor will destroy portions of the bone and aggressively grow, pushing into the surrounding soft tissues. This is why some patients can feel a bony bump through the skin.

Other imaging scans. Doctors usually also request computed tomography (CT) scans or magnetic resonance imaging (MRI) scans to help further define the tumor. These scans can provide more detail, especially of soft tissues. They can also provide cross-sectional images.

(Left) An x-ray image of a CMF located at the top end of the tibia. (Center) An MRI image of the same tumor. (Right) A cross-section MRI image of the same tumor. Note how the tumor has grown beyond the bone.

Biopsy. A biopsy is often necessary to confirm the diagnosis of CMF. In a biopsy, a tissue sample of the tumor is taken and examined under a microscope. Your doctor may give you a local anesthetic to numb the area and take a sample using a needle. Biopsies can also be performed as a small operation.

Under a microscope, chondromyxoid fibromas have elements of benign cartilage (chondroid), myxoid, and fibrous tissue.

The typical appearance of a CMF under a microscope.

Differential Diagnosis

The imaging and tissue tests help your doctor differentiate CMF from other tumors that have a similar appearance, such as giant cell tumor, enchondroma, chondroma, nonossifying fibroma, aneurysmal bone cyst, or infection of the bone (osteomyelitis).

It is very important in planning treatment to differentiate CMF from more aggressive, cancerous tumors like chondrosarcoma or osteosarcoma.

Curettage

The most common method of treating CMF is with curettage. In this procedure, the tumor is scraped out of the bone.

After curettage, your doctor may fill the hole with a bone graft — this is bone taken from a donor (allograft) or from another bone in your body (autograft). Sometimes, additional chemicals, such as phenol or liquid nitrogen, are placed inside the bone cavity to try to reduce the risk of the tumor growing back.

Surgical Complications

Recurrence of the tumor is the most serious complication of treatment. Even when these tumors are adequately treated, they grow back in the same location up to 25% of the time. More aggressive surgery — such as removing greater portions of the bone — will lessen the chance of the tumor coming back, but may have a higher chance of causing complications or permanently damaging the bone.

Other complications include infection and, rarely, fracture of the bone through the treated area.

How long it will take to return to all your daily activities will vary depending on where the tumor was located. If you have any pain or discomfort, you may want to limit some activity. Your doctor will provide you with specific instructions to guide your recovery.

Your doctor will monitor you and take routine x-rays for a few years after your surgery to check for tumor recurrence.. Should the tumor come back, it can be treated using the same methods. Your doctor will talk to you about all the options.

AAOS does not endorse any treatments, procedures, products, or physicians referenced herein. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific orthopaedic advice or assistance should consult his or her orthopaedic surgeon, or locate one in your area through the AAOS "Find an Orthopaedist" program on this website.